This invention relates generally to mounting devices which function to transfer heat from a source, such as an electronic device, to a heat sink.
In the design of a power converter, printed circuit boards, with electronic devices affixed thereto, were thermally attached to a chassis. Air passages were used to direct cooling air over and under the printed circuit boards to further aid in the heat removal process. A problem occurred when a plurality of power modules, each having an aluminum plate with encapsulated electronic components mounted to one surface of the plate and several contact pins extending from the encapsulated electronic components opposite the surface mounted to the plate, had to be connected to the printed circuit board. The aluminum plate had to face away from the printed circuit board and the chassis to permit the power modules' contact pins to be connected to conductors on the printed circuit board. The chassis would provide an excellent heat sink but the chassis was mounted below the printed circuit board and the aluminum plate thus would be on the side of the power module farthest from the printed circuit board. The surface temperature of the aluminum plate, during the operation of the power module, was such that it had to be cooled. Applying conventional heat sinks to the aluminum plate makes the replacement, addition, or deletion of power modules from the circuit board difficult.
The prior art approach to heat transfer problems is exemplified by the arrangement shown in U.S. Pat. No. 3,518,493 entitled "Arrangement for Mounting and Connecting Microelectronic Circuits", by J. R. Bathrick, Jr. et al. In this patent there is disclosed a heat sink that is formed from a pair of parallel elongated metal strips. Electronic components are placed in thermal contact with the outer sides of the metal strips and printed circuit boards are positioned along the top and the bottom edges of the elongated metal strips with conductors running therebetween. This particular arrangement does not allow for an easy removal of the electronic components nor does it allow for the addition of components if desired.
Another heat sink of interest is disclosed in U.S. Pat. No. 3,676,745 entitled "Electronic Assembly Utilizing Thermal Panel for Heat Sink", by J. C. Traweek. In this patent heat developing components are affixed to both surfaces of a printed circuit board. The largest heat generators are encapsulated in blocks of electrically insulating, thermally conductive material. The blocks are then sandwiched between a metal chassis and the printed circuit board. The chassis, because of its size, functions as a superior heat sink.
Another patent of interest is U.S. Pat. No. 4,104,700 entitled "Heat Pipe Cooling of Semiconductor Device Packaging Systems", by R.V. Hutchison et al. In this patent heat sinks having posts which cooperate with hold down clamps, clamp heat sink plates attached to integrated circuit packages to printed circuit board heat sinks. Heat pipes and a plenum chamber through which air is circulated, are used to dissipate heat to the ambient air.
Another patent of interest is U.S. Pat. No. 4,535,385 entitled "Circuit Module with Enhanced Heat Transfer and Distribution", by M. C. August et al. In this patent printed circuit boards are mounted in a closely spaced relationship on opposite sides of a flat plate heat sink. Electrical devices, mounted to the surface of the printed circuit boards farthest from the flat plate heat sink, are thermally connected to the heat sink by means of plated-through holes and thermally conductive pads which project through holes in the printed circuit boards to contact the electrical device on one end and the flat plate heat sink on the other end.
A solution to applicants' problem is not readily discernible from a review of the prior art. The problem restated is, how to connect an electronic module, having a metal plate on one surface, to a chassis heat sink which is positioned on the opposite side of a printed circuit board when the electronic module has connectors that must make contact with conductors on the printed circuit board.